Coordination Chemistry

Step 1: Transition Elements and Their Properties.
Transition elements have partially filled d-orbitals, which make them capable of forming coordinate bonds with ligands. The ability to form complex compounds arises from their ability to accept electron pairs from ligands, resulting in the formation of stable coordination complexes.
Step 2: Explanation.
- Transition elements typically have variable oxidation states, which also enhances their ability to form complexes.
- The small size and high charge density of transition metal ions allow them to interact strongly with ligands, forming stable coordination compounds.
Step 3: Example.
For example, the complex [Cu(NH₃)₄]²⁺ is formed when copper(II) ion (Cu²⁺) interacts with ammonia (NH₃) molecules, resulting in the formation of a square planar complex.

Step 1: Definition of Effective Atomic Number (EAN).
The effective atomic number (EAN) is the total number of electrons around a metal ion in a coordination complex, including the electrons donated by the ligands. It is used to assess the stability of transition metal complexes, particularly when the metal follows the 18-electron rule, which is a guideline for predicting the stability of organometallic compounds.
Step 2: Calculation of EAN.
The effective atomic number is calculated as:
Step 3: Example.
For the complex , Ni is in the zero oxidation state, and each CO ligand donates two electrons. The EAN of Ni in this complex would be: